Large-scale agricultural burning and cardiorespiratory emergency department visits in the U.S. state of Kansas

BACKGROUND: Prescribed agricultural burning is a common land management practice, but little is known about the health effects from the resulting smoke exposure. OBJECTIVE: To examine the association between smoke from prescribed burning and cardiorespiratory outcomes in the U.S. state of Kansas. METHODS: We analyzed a zip code-level, daily time series of primary cardiorespiratory emergency department (ED) visits for February–May (months when prescribed burning is common in Kansas) in the years 2009–2011 (n=109,220). Given limited monitoring data, we formulated a measure of smoke exposure using non-traditional datasets, including fire radiative power and locational attributes from remote sensing data sources. We then assigned a population-weighted potential smoke impact factor (PSIF) to each zip code, based on fire intensity, smoke transport, and fire proximity. We used Poisson generalized linear models to estimate the association between PSIF on the same day and in the past 3 days and asthma, respiratory including asthma, and cardiovascular ED visits. RESULTS: During the study period, prescribed burning took place on approximately 8 million acres in Kansas. Same-day PSIF was associated with a 7% increase in the rate of asthma ED visits when adjusting for month, year, zip code, meteorology, day of week, holidays, and correlation within zip codes (rate ratio [RR]: 1.07; 95% confidence interval [CI]: 1.01, 1.13). Same-day PSIF was not associated with a combined outcome of respiratory ED visits (RR [95% CI]: 0.99 [0.97, 1.02]), or cardiovascular ED visits (RR [95% CI]: 1.01 [0.98, 1.04]). There was no consistent association between PSIF during the past 3 days and any of the outcomes. SIGNIFICANCE: These results suggest an association between smoke exposure and asthma ED visits on the same day. Elucidating these associations will help guide public health programs that address population-level exposure to smoke from prescribed burning. IMPACT STATEMENT: In this time series study, we examined the health effects of smoke exposure from prescribed agricultural burning in Kansas. Our findings suggest an association between smoke from prescribed burning and emergency department visits for asthma, but not for cardiovascular outcomes.